A cubic boron nitride (hereinafter referred to as “cBN”) sintered body has the second highest hardness next to diamond and has a feature of not reacting with an iron-based material, and is therefore conventionally used in a cutting tool for an iron-based material (Japanese Patent Laying-Open No. 2011-207690 for example).
It is considerably difficult to directly sinter cBN particles (powder) alone, and therefore, a cBN sintered body commonly used in a cutting tool is manufactured by using a ceramic material such as TiC or TiN as a binder and sintering a cBN powder under a ultrahigh pressure.
Further, the conventional cBN sintered body contains, in some cases, a catalyst element which is at least one selected from the group consisting of cobalt (Co), chromium (Cr), nickel (Ni), and molybdenum (Mo) for the purpose of improving the fracture resistance. In this case, the catalyst element is added for the purpose of improving the toughness of the cBN sintered body to thereby improve the fracture resistance. The catalyst element is a metal element and thus has ductility. The ductility, however, makes it difficult to mill and mix the catalyst element with the cBN powder.
In view of the above, the conventional cBN sintered body is produced in the following way. Namely, a powdered catalyst element is prepared by using a catalyst element in the form of a compound such as carbide or nitride, and a mixture of the catalyst element powder and a cBN powder is sintered.